JP2011046591A - Optical glass, preform for precision press molding, optical element, methods for production thereof, and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-refractive index, highly-dispersible optical glass excellent in devitrification resistance and precision press-molding property. <P>SOLUTION: The optical glass is an oxide glass and comprises, by cationic%, 20-40% of the total of Si<SP>4+</SP>and B<SP>3+</SP>, 15-40% of the total of Nb<SP>5+</SP>, Ti<SP>4+</SP>, W<SP>6+</SP>and Zr<SP>4+</SP>, 0.2-20% of the total of Zn<SP>2+</SP>, Ba<SP>2+</SP>, Sr<SP>2+</SP>and Ca<SP>2+</SP>, and 15-55% of the total of Li<SP>+</SP>, Na<SP>+</SP>and K<SP>+</SP>. The optical glass has: the cationic ratio of the content of B<SP>3+</SP>to the total content of B<SP>3+</SP>and Si<SP>4+</SP>being 0.01-0.5, that of Zr<SP>4+</SP>to the total of Nb<SP>5+</SP>, Ti<SP>4+</SP>, W<SP>6+</SP>and Zr<SP>4+</SP>being 0.05 or less; the molar ratio of the total content of Zn<SP>2+</SP>and Ba<SP>2+</SP>to the total content of Zn<SP>2+</SP>, Ba<SP>2+</SP>, Sr<SP>2+</SP>and Ca<SP>2+</SP>being 0.8-1; a refractive index nd of 1.815 or more; and an Abbe's number νd of 29 or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides an optical glass having a high refractive index and a high dispersion characteristic and having an excellent precision press moldability, a precision press molding preform and optical element made of the glass, a manufacturing method thereof, and the optical element. The present invention relates to a mounted imaging apparatus.

  High-refractive index, high-dispersion optical glass is in high demand, and an aspherical lens made of the glass is indispensable as a lens for a high-performance digital still camera.

  As a method for mass-producing aspherical lenses, a precision press molding method (also called a mold optics press method) is known. Phosphate glass is known as a high refractive index and high dispersion optical glass that can be molded by a precision press molding method. Phosphate-based optical glass is an excellent glass, but has a problem that the glass surface is easily damaged during precision press molding.

  Glasses disclosed in Patent Documents 1 to 5 are known as non-phosphate high refractive index and high dispersion optical glass. All of these glasses have a silica-based composition.

International Publication No. 2004-110842 JP 2004-161598 A Japanese Patent Laid-Open No. 2002-87841

  In order to obtain a high refractive index and high dispersion optical glass, it is necessary to introduce a component that imparts high refractive index and high dispersion, such as Nb and Ti, regardless of whether it is phosphate-based or silica-based.

  However, when glass containing Nb, Ti or the like is precision press-molded, an oxidation-reduction reaction occurs at the interface between the glass and the press mold, and as a result, foaming occurs on the lens surface, which can maintain the production yield at a high level. The problem that it is not easy occurs. These problems become apparent when the press molding temperature becomes high, but silica glass has a higher glass transition temperature than phosphate glass, and the press molding temperature must be increased. The reaction between the glass and the press mold is encouraged.

For example, the glass disclosed in Patent Document 1 has a glass transition temperature of 530 ° C. or higher, which is insufficient as a glass transition temperature for suppressing the above reaction. In addition, the glass stability is low, crystals are precipitated while stirring the glass melt to obtain a homogeneous optical glass, or crystals are precipitated when the molten glass is cast into a mold, etc. This glass is not suitable for mass production.
Similarly to Patent Document 1, the glass disclosed in Patent Document 2 has a problem of low glass stability and easy devitrification.
Patent Document 3 discloses a high-refractive index high-dispersion glass and a medium-refractive index high-dispersion glass, but the glass transition temperature is not sufficiently lowered for the high-refractive index high-dispersion glass.

  Under such circumstances, it is expected to realize a high refractive index and high dispersion optical glass that is not easily devitrified and can stably produce high quality optical elements by precision press molding.

  The present invention solves the above problems, and has a high refractive index and high dispersion optical glass excellent in devitrification resistance and precision press moldability, a precision press molding preform and optical element comprising the optical glass, and production thereof. It is an object of the present invention to provide a method and an imaging device including the optical element.

Means for solving the problems in the present invention are:
[1] Oxide glass, expressed in cation%,
Si ⁴⁺ and B ³⁺ in total 20 to 40%,
Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ in total 15-40%,
Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ in total 0.2 to 20%,
Li ⁺ , Na ⁺ and K ⁺ in total 15-55%,
Including
The cation ratio of the content of B ³⁺ to the total content of B ³⁺ and Si ⁴⁺ is 0.01 to 0.5,
The cation ratio of the Zr ⁴⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ is 0.05 or less,
The molar ratio of the total content of Zn ²⁺ and Ba ^{2+ to} the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ is 0.8 to 1,
An optical glass having a refractive index nd of 1.815 or more and an Abbe number νd of 29 or less,
[2] The optical glass according to the above [1], wherein the glass transition temperature is less than 530 ° C.
[3] The optical glass according to [1] or [2], wherein the liquidus temperature is 1080 ° C. or lower,
[4] Items [1] to [3] above, wherein the cation ratio of the content of Nb ⁵⁺ to the total content of Nb ⁵⁺ and Ti ⁴⁺ (Nb ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ )) is 0.65-1. The optical glass according to any one of
[5] The optical glass according to any one of [1] to [4], wherein the content of Si ⁴⁺ is 15 to 30%,
[6] The optical glass according to any one of [1] to [5], wherein the content of B ³⁺ is 15% or less,
[7] The optical glass according to any one of [1] to [6], wherein the content of Nb ⁵⁺ is 10 to 30%.
[8] The optical glass according to any one of [1] to [7], wherein the content of Ti ⁴⁺ is 0 to 15%,
[9] The optical glass according to any one of [1] to [8] above, wherein the content of W ⁶⁺ is 0 to 4%.
[10] The optical glass according to any one of [1] to [9], wherein the content of Zr ⁴⁺ is 0 to 4%,
[11] The optical glass according to any one of [1] to [10], wherein the content of Zn ²⁺ is 9% or less,
[12] The optical glass according to any one of [1] to [11], wherein the content of Ba ²⁺ is 6% or less.
[13] The optical glass according to any one of [1] to [12], wherein the content of Sr ²⁺ is 2% or less,
[14] The optical glass according to any one of [1] to [13], wherein the content of Ca ²⁺ is 3% or less.
[15] The optical glass according to any one of [1] to [14], wherein the content of Li ⁺ is 25% or less,
[16] The optical glass according to any one of [1] to [15], wherein the content of Na ⁺ is 30% or less,
[17] The optical glass according to any one of [1] to [16], wherein the K ⁺ content is 25% or less,
[18] The optical glass according to any one of [1] to [17], wherein the cation ratio of the Li ⁺ content to the total content of Li ⁺ , Na ⁺ and K ⁺ is 0.1 to 1. .
[19] The optical glass according to any one of [1] to [18], wherein ΔPg, F is 0.0130 or less.
[20] A precision press-molding preform comprising the optical glass according to any one of [1] to [19] above,
[21] A method for producing a precision press-molding preform for producing a preform according to the above-mentioned [21], wherein a glass raw material is heated and melted to produce a molten glass, and the molten glass is molded.
[22] An optical element comprising the optical glass according to any one of [1] to [19] above,
[23] A method for manufacturing an optical element comprising a step of heating the precision press-molding preform according to the above [20], and performing precision press molding using a press mold,
[24] The method for producing an optical element according to the above [23], wherein the precision press molding preform and the press mold are heated together to perform precision press molding,
[25] The method for manufacturing an optical element according to the above [23], wherein the precision press-molding preform is heated and then introduced into a preheated press mold and precision press-molded.
[26] An imaging device comprising the optical element according to [22] above,
It is.

  According to the present invention, a high-refractive index, high-dispersion optical glass excellent in devitrification resistance and precision press moldability, a precision press-molding preform and optical element made of the optical glass, a production method thereof, and the above An imaging device including an optical element can be provided.

6 is a photograph of a lens obtained in Comparative Example 2.

[Optical glass]
In the optical glass of the present invention, by adopting a silica-based composition, the glass surface is prevented from being scratched during precision press molding and is a problem inherent to precision press molding of high refractive index and high dispersion optical glass. In order to prevent degradation of the optical element surface quality due to the interfacial reaction between the high refractive index and high dispersion imparting component and the molding surface of the press mold, the glass transition temperature is further lowered while maintaining a high refractive index. Provided is a high refractive index, high dispersion optical glass capable of stably producing quality optical elements. In addition, an optical glass that provides excellent glass stability and is easy to manufacture while being a high refractive index glass is provided.

  Furthermore, while maintaining the high refractive index and high dispersion characteristics, the partial dispersion ratios Pg and F are kept small, and the characteristics close to the standard line (normal line) in the partial dispersion ratios Pg and F-Abbe number νd are given. By combining with a lens made of dispersion glass, an optical glass material that is very effective for correcting higher-order chromatic aberration is provided. The silica-based composition is preferable from the viewpoint of realizing such partial dispersion characteristics.

The optical glass of the present invention completed based on such a concept is
Oxide glass, expressed as cation%,
Si ⁴⁺ and B ³⁺ in total 20 to 40%,
Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ in total 15-40%,
Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ in total 0.2 to 20%,
Li ⁺ , Na ⁺ and K ⁺ in total 15-55%,
Including
The cation ratio of the content of B ³⁺ to the total content of B ³⁺ and Si ⁴⁺ is 0.01 to 0.5,
The cation ratio of the Zr ⁴⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ is 0.05 or less,
The molar ratio of the total content of Zn ²⁺ and Ba ^{2+ to} the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ is 0.8 to 1,
And an optical glass having a refractive index nd of 1.815 or more and an Abbe number νd of 29 or less.

  Hereinafter, the optical glass of the present invention will be described in detail. Hereinafter, the content and total content of each cation component are expressed as cation% unless otherwise specified.

Si ⁴⁺ and B ³⁺ are glass network-forming oxides, and are necessary components for maintaining glass stability and moldability of molten glass. However, when these components are excessively contained, the refractive index decreases. ^Therefore , the total content of Si ⁴⁺ and B ³⁺ is set to 20 to 40%. A preferable range of the total content of Si ⁴⁺ and B ³⁺ is 25 to 35%, a more preferable range is 25 to 34%, a further preferable range is 29 to 33%, and a still more preferable range is 30 to 33%.

In addition to the above effects, Si ⁴⁺ has the effect of suppressing phase separation during precision press molding, improves chemical durability, suppresses viscosity reduction during molten glass molding, and maintains a state suitable for molding. However, excessive introduction increases the glass transition temperature and the liquidus temperature, and decreases the meltability and devitrification resistance. By suppressing the phase separation, it is possible to prevent a decrease in transmittance due to white turbidity of the glass.

B ³⁺ has the functions of improving the meltability and lowering the glass transition temperature in addition to the above effects, but the chemical durability is lowered by introducing it excessively. By improving the meltability, a homogeneous glass can be obtained without increasing the glass melting temperature. As a result, the erosion of the crucible can be suppressed and the coloring of the glass due to the melting of the material such as platinum constituting the crucible can be suppressed.

Considering the effects of Si ⁴⁺ and B ³⁺ , the cation ratio of the content of B ³⁺ to the total content of B ³⁺ and Si ⁴⁺ (B ³⁺ / (B ³⁺ + Si ⁴⁺ )) is 0.01 to 0.5. To do. By setting the cation ratio (B ³⁺ / (B ³⁺ + Si ⁴⁺ )) to 0.01 or more, the glass transition temperature can be further lowered, and the effect of suppressing the interfacial reaction between the glass and the press mold during precision press molding can be enhanced. In addition, the meltability and devitrification resistance can be improved. However, when the cation ratio (B ³⁺ / (B ³⁺ + Si ⁴⁺ )) is greater than 0.5, the viscosity during molten glass molding decreases, the molten glass moldability deteriorates, or the phase separation tendency during precision press molding Increases or chemical durability decreases. The preferable range of the cation ratio (B ³⁺ / (B ³⁺ + Si ⁴⁺ )) is 0.05 to 0.5, the more preferable range is 0.08 to 0.5, and the further preferable range is 0.1 to 0.5. A preferable range is 0.1 to 0.45, and an even more preferable range is 0.1 to 0.4.

In addition, the preferable range of the content of Si ⁴⁺ is 15 to 30%, the more preferable range is 19 to 26%, the further preferable range is 19 to 25.5%, and the preferable range of the content of B ³⁺ is 15% or less. A more preferable range is 0.3 to 15%, a further preferable range is 0.5 to 15%, a more preferable range is 1 to 15%, a still more preferable range is 3 to 15%, and an even more preferable range is 6 to 12%. .3%, and an even more preferred range is 7-12%.

Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ are all components that have a great effect on high refractive index and high dispersion. If the total content of these components is less than 15%, it will be difficult to obtain the required refractive index, and if it exceeds 40%, the devitrification resistance will decrease and the liquidus temperature will increase. Therefore, the total content of Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ is set to 15 to 40%. A preferable range of the total content is 25 to 35%, a more preferable range is 26 to 33%, a further preferable range is 28 to 31%, and a further preferable range is 28 to 30%.

Nb ⁵⁺ has the function of improving devitrification resistance and lowering the liquidus temperature in addition to the above effects. Further, it works to bring the partial dispersion characteristic closer to the normal line, that is, to make ΔPg, F close to zero. However, if it is excessively contained, the devitrification resistance decreases and the liquidus temperature rises.

Ti ⁴⁺ functions to improve devitrification resistance and chemical durability in addition to the above effects. However, when it is excessively contained, the phase separation tendency during precision press molding increases.

W ⁶⁺ serves to improve devitrification resistance and suppress increase in liquidus temperature in addition to the above effects. However, when it is contained excessively, devitrification resistance deteriorates and liquidus temperature rises. Moreover, coloring tends to increase.

In addition to the above-mentioned effects of Zr ⁴⁺ , it functions to suppress phase separation during precision press molding and to improve chemical durability and devitrification resistance. The liquidus temperature rises. The excessive introduction of Zr ⁴⁺ increases the glass transition temperature and promotes the interfacial reaction between the glass and the press mold during precision press molding, so the total content of Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ The cation ratio of the content of Zr ⁴⁺ to Zr ⁴⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + W ⁶⁺ + Zr ⁴⁺ ) is 0.05 or less. From the viewpoint of obtaining the above effect due to the inclusion of Zr ⁴⁺ , the range of the cation ratio (Zr ⁴⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + W ⁶⁺ + Zr ⁴⁺ )) is preferably 0.005 to 0.05, preferably 0.008 to 0 0.03 is more preferable, and 0.009 to 0.025 is even more preferable.

Among Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ , and Zr ⁴⁺ , Nb ⁵⁺ and Ti ⁴⁺ are components whose devitrification resistance is unlikely to deteriorate even when introduced in a large amount. ^Therefore , the total content of Nb ⁵⁺ and Ti ⁴⁺ The range is preferably 20 to 35%, more preferably 26 to 29.5%, and still more preferably 26 to 28.5%. Further, Nb ⁵⁺ and Ti ⁴⁺ are essential components from the viewpoint of further improving the devitrification resistance.

^Furthermore, Nb 5+, of ^{Ti 4+,} suppressed towards the ^{Nb 5+} low partial dispersion ratio, larger works to bring the partial dispersion property to the normal line, the ^{Nb 5+} content to the total content of ^{Nb 5+} and ^{Ti 4+} The cation ratio (Nb ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ )) is preferably in the range of 0.65 to 1. However, since devitrification resistance is improved by coexisting Nb ⁵⁺ and Ti ⁴⁺ as glass components, the cation ratio (Nb ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ )) should be in the range of 0.65 to 0.9. Is more preferable, and a range of 0.7 to 0.8 is more preferable.

Considering each effect of Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ , the preferred ranges of the respective component amounts are as follows.

A preferable upper limit of the Nb ⁵⁺ content is 30%, a more preferable upper limit is 23%, a still more preferable upper limit is 22%, and a more preferable upper limit is 21%. A preferable lower limit of the Nb ⁵⁺ content is 10%, and a more preferable lower limit. Is 16%, a more preferred lower limit is 18%, and a more preferred lower limit is 19%. The preferable combination of the upper limit and the lower limit is arbitrary. As a specific example, the preferable range of the content of Nb ⁵⁺ is 10 to 30%, the more preferable range is 16 to 23%, the still more preferable range is 18 to 22%, and the still more preferable range is 19 to 21%.

The preferable upper limit of the content of Ti ⁴⁺ is 15%, the more preferable upper limit is 12%, the further preferable upper limit is 10%, the still more preferable upper limit is 9.5%, the still more preferable upper limit is 9%, and the still more preferable upper limit is 8. 5%, an even more preferable upper limit is 8.0, a preferable lower limit of the content of Ti ⁴⁺ is 1%, a more preferable lower limit is 2%, a further preferable lower limit is 3%, a more preferable lower limit is 4%, and even more preferable. The lower limit is 5%, and an even more preferable lower limit is 5.5%. The preferable combination of the upper limit and the lower limit is arbitrary. As a specific example, the preferable range of the content of Ti ⁴⁺ is 0 to 15%, the more preferable range is 0 to 12%, the further preferable range is 0 to 10%, the more preferable range is 1 to 10%, and the more preferable range. Is 2 to 10%, still more preferably 3 to 9%, still more preferably 4 to 9%, still more preferably 5 to 8.5%, and particularly preferably 5.5 to 8.0%. is there.

The preferable upper limit of the content of W ⁶⁺ is 4%, the more preferable upper limit is 3%, the further preferable upper limit is 2.5%, the more preferable upper limit is 2.0%, and the still more preferable upper limit is 1.5%. A preferable lower limit of the ⁶⁺ content is 0.5%. The preferable combination of the upper limit and the lower limit is arbitrary. As a specific example, a preferable range of the content of W ⁶⁺ is 0 to 3%, a more preferable range is 0 to 2.5%, a further preferable range is 0.5 to 2.0%, and a more preferable range is 0.5. ~ 1.5%.

The preferable upper limit of the content of Zr ⁴⁺ is 4%, the more preferable upper limit is 3%, the further preferable upper limit is 2%, the more preferable upper limit is 1.5%, the still more preferable upper limit is 1.2%, and the more preferable upper limit is 1. %, A more preferable upper limit is 0.6%, a preferable lower limit of the content of Zr ⁴⁺ is 0.2%, and a more preferable lower limit is 0.5%. The preferable combination of the upper limit and the lower limit is arbitrary. As a specific example, a preferable range of the content of Zr ⁴⁺ is 0 to 4%, a more preferable range is 0 to 3%, a further preferable range is 0 to 2%, a more preferable range is 0 to 1.5%, and a much more preferable range. A preferred range is 0.1-1.5%, an even more preferred range is 0.2-1.2%, an even more preferred range is 0.2-1%, and an even more preferred range is 0.4-0. 6%.

Zn ²⁺ , Ba ²⁺ , Sr ²⁺ , and Ca ²⁺ are useful for adjusting optical constants, increase devitrification resistance, meltability, and light transmittance, and are added to glass raw materials as carbonates and nitrates to clarify the effect. It is a component which can raise. When the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ is less than 0.5%, it is difficult to obtain the above effect, and when it exceeds 20%, the devitrification resistance is lowered and the liquidus temperature is increased. In addition, chemical durability is reduced. Therefore, the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ is set to 0.2 to 20%. A preferable upper limit of the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ is 15%, a more preferable upper limit is 10%, and a further preferable upper limit is 8.5%. Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca The preferred lower limit of the total content of ²⁺ is 0.3%, the more preferred lower limit is 0.4%, the still more preferred lower limit is 0.5%, the still more preferred lower limit is 1%, the still more preferred lower limit is 3%, and still more preferred. The lower limit is 5%, an even more preferable lower limit is 6.5%, and an even more preferable upper limit is 7%. The preferable combination of the upper limit and the lower limit is arbitrary. As a specific example, a preferable range of the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ is 1 to 20%, a more preferable range is 3 to 20%, a further preferable range is 3 to 15%, and a more preferable range. Is 5 to 10%, a more preferable range is 6.5 to 10%, and a further preferable range is 7 to 8.5%.

In addition to the above effects, Zn ²⁺ is excellent in the function of lowering the glass transition temperature and also has the function of maintaining the refractive index in a high state. However, when it contains excessively, devitrification resistance falls, liquid phase temperature rises, or the chemical durability tends to fall.

In addition to the above effects, Ba ²⁺ has a function of increasing the refractive index and suppressing phase separation during precision press molding. However, when it contains excessively, devitrification resistance falls, liquid phase temperature rises, or the chemical durability tends to fall.

In addition to the above effects, Sr ²⁺ functions to increase the refractive index although the effect is smaller than that of Ba ²⁺ . It also has the function of suppressing phase separation during precision press molding. However, when it contains excessively, devitrification resistance falls, liquid phase temperature rises, or the chemical durability tends to fall.

In addition to the above effects, Ca ²⁺ functions to suppress phase separation during precision press molding. However, when it is contained excessively, the devitrification resistance decreases, the liquidus temperature increases, the glass transition temperature increases, and the chemical durability tends to decrease.

Among Zn ²⁺ , Ba ²⁺ , Sr ²⁺ , and Ca ²⁺ , Zn ²⁺ is a component that has a large effect of lowering the glass transition temperature while maintaining a high refractive index, and Ba ²⁺ is a component that greatly increases the refractive index. Therefore, in order to achieve both high refractive index and low glass transition temperature, the cation ratio of the total content of Zn ²⁺ and Ba ^{2+ to} the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ ((Zn ²⁺ + Ba ²⁺ ) / (Zn ²⁺ + Ba ²⁺ + Sr ²⁺ + Ca ²⁺ )) is set to 0.8-1.

The preferable range of the cation ratio ((Zn ²⁺ + Ba ²⁺ ) / (Zn ²⁺ + Ba ²⁺ + Sr ²⁺ + Ca ²⁺ )) is 0.82-1, more preferable range is 0.85-1, and further preferable range is 0.9-1. It is.

Considering each effect of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ , and Ca ²⁺ , preferred ranges of the respective component amounts are as follows.
The preferable range of the Zn ²⁺ content is 9% or less, the more preferable range is 1 to 9%, the further preferable range is 3 to 9%, the more preferable range is 3 to 8%, and the still more preferable range is 4.5 to 6 0.5%, and an even more preferable range is 5.0 to 6.0%, a preferable range of the Ba ²⁺ content is 6% or less, a more preferable range is 0.5 to 6%, and a further preferable range is 0.00. 5 to 4%, more preferable range is 0.8 to 3%, even more preferable range is 1.0 to 2.0%, preferable range of Sr ²⁺ content is 0 to 2%, more preferable range is 0 to 1.5%, more preferably 0 to 1%, Ca ²⁺ content is preferably 0 to 3%, more preferably 0 to 2%, and still more preferably 0 to 1.5%. %, More preferred range is 0.1-0.9%, even more preferred A new range is 0.32 to 0.45%.

Li ⁺ , Na ⁺ and K ⁺ are components having an effect of improving the meltability and lowering the glass transition temperature. When the total content of these components is less than 15%, it becomes difficult to obtain the above effect, and when it exceeds 55%, the glass stability is lowered and the liquidus temperature is increased. Therefore, the total content of Li ⁺ , Na ⁺ and K ⁺ is 15 to 55%. A preferable range of the total content of Li ⁺ , Na ⁺ and K ⁺ is 20 to 50%, a more preferable range is 25 to 40%, a further preferable range is 28 to 40%, and a more preferable range is 30 to 35%.

Li ⁺ is the component that has the greatest effect of lowering the glass transition temperature while maintaining a high refractive index among the alkali metal components. However, when excessively contained, the glass stability is lowered and the liquidus temperature is increased. To do.

In addition to the above effects, Na ⁺ and K ⁺ work to further increase the glass stability by the mixed alkali effect by coexisting with Li ⁺ .

In order to achieve both high refractive index and low glass transition temperature, in the present invention, the cation ratio of the content of Li ⁺ to the total content of Li ⁺ , Na ⁺ and K ⁺ (Li ⁺ / (Li ⁺ + Na ⁺ + K ⁺ )) Is preferably 0.1-1. From the above viewpoint, the more preferable range of the cation ratio (Li ⁺ / (Li ⁺ + Na ⁺ + K ⁺ )) is 0.2 to 1, more preferably 0.3 to 0.8, and still more preferably 0.4 to 0. .5.

Considering each effect of Li ⁺ , Na ⁺ , K ⁺ , the preferred ranges of the respective component amounts are as follows.
The preferable range of the Li ⁺ content is 25% or less, the more preferable range is 10 to 20%, the further preferable range is 13 to 17%, and the more preferable range is 14 to 16%. The preferable range of the Na ⁺ content is Is 30% or less, a more preferable range is 10 to 20%, a further preferable range is 13 to 17%, a still more preferable range is 14 to 16%, and a preferable range of the content of K ⁺ is 0 to 25%, and more preferable. The range is 0 to 20%, the more preferable range is 0 to 15%, more preferably 0 to 9%, the still more preferable range is 0 to 5%, and the still more preferable range is 2 to 4%.

La ³⁺ , Gd ³⁺ , Y ³⁺ and Yb ³⁺ work to increase the refractive index and improve the chemical durability, but when introduced in excess of 6%, the liquidus temperature rises and the devitrification resistance increases. descend. Therefore, each content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ is set to 0 to 6%. The preferred range of the content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Yb ³⁺ is 0 to 3%, more preferred range is 0 to 2%, and more preferred range is 0 to 1%, even more preferred. Does not introduce La ³⁺ , Gd ³⁺ , Y ³⁺ , or Yb ³⁺ .

Ta ⁵⁺ also functions to increase the refractive index and improve the chemical durability, but when introduced in excess of 3%, the liquidus temperature increases and the devitrification resistance decreases. Therefore, the content of Ta ⁵⁺ is set to 0 to 3%. A preferable range of the content of Ta ⁵⁺ is 0 to 2%, and a more preferable range is 0 to 1%.

Ge ⁴⁺ is a network-forming oxide and also functions to increase the refractive index. However, since it is an extremely expensive component, the content of Ge ⁴⁺ is 0 to 2%, preferably 0 to 1%. More preferably, no Ge ⁴⁺ is introduced.

Bi ³⁺ functions to increase the refractive index and improve the glass stability. However, when introduced in excess of 2%, the coloration of the glass is strengthened, so the content of Bi ³⁺ is 0 to 2%, preferably 0 to 0%. 1%, more preferably not contained.

Al ³⁺ works to improve glass stability and chemical durability if it is in a small amount, but if it is introduced in excess of 1%, the liquidus temperature rises and devitrification resistance decreases. Therefore, the content of Al ³⁺ is 0 to 1%, preferably 0 to 0.5%, more preferably 0 to 0.2%, and even more preferably not contained.

The glass of the present invention does not need to contain components such as Ga ³⁺ , Lu ³⁺ and Hf ⁴⁺ . Since Ga ³⁺ , Lu ³⁺ , and Hf ⁴⁺ are also expensive components, the contents of Ga ³⁺ , Lu ³⁺ , and Hf ⁴⁺ are preferably suppressed to 0 to 1%, respectively, and each is suppressed to 0 to 0.5%. More preferably, it is more preferable to suppress each to 0 to 0.1%, and it is particularly preferable that Ga ³⁺ is not introduced, Lu ³⁺ is not introduced, and Hf ⁴⁺ is not introduced.

  In consideration of environmental impact, it is preferable not to introduce As, Pb, U, Th, Te, or Cd.

Furthermore, from the viewpoint of taking advantage of the excellent light transmittance of the glass, do not introduce substances that cause coloring such as Cu, Cr, V, Fe, Ni, Co, that is, do not use these substances as glass raw materials during glass production. It is preferable. In order to achieve the object of the present invention, the sum of Si ⁴⁺ , B ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Ba ²⁺ , Sr ²⁺ , Ca ²⁺ , Li ⁺ , Na ⁺ and K ⁺ The content is preferably 95 to 100%, more preferably 98 to 100%, and still more preferably 99 to 100%.

In the optical glass of the present invention, 0 to 2% by mass of Sb ₂ O ₃ and 0 to 2% by mass of SnO ₂ can be added on an external basis in terms of oxides. These additives function as a fining agent, and Sb ₂ O ₃ can suppress the coloring of the glass due to the mixing of impurities such as Fe. Preferable addition amounts of Sb ₂ O ₃ and SnO ₂ are 0 to 1% by mass, more preferably 0 to 0.5% by mass, respectively.

The optical glass of the present invention is an oxide glass, and among the anion components, 50 anion% or more is O ²⁻ . In addition, a small amount of F ⁻ , Cl ⁻ , I ⁻ and Br ⁻ may be introduced. A preferable range of the content of O ²⁻ is 50 to 100 anion%, a more preferable range is 80 to 100 anion%, further preferably 85 to 100 anion%, more preferably 90 to 100 anion%, still more preferably 95 to 100%, still more preferably 98 to 100 anion%, still more preferably 99 to 100 anion%, particularly preferably 100 anion%.

[Refractive index, Abbe number]
The optical glass of the present invention has a refractive index nd of 1.83 or more and an Abbe number νd of 29 or less. By setting the refractive index nd within the above range, it is possible to obtain an optical glass suitable for a material of an optical element constituting a high-function and compact optical system. By using high refractive index glass, the curvature of the lens surface can be relaxed when producing lenses having the same light collecting power. As a result, it is possible to improve moldability when the lens is precision press-molded.

  By setting the Abbe number νd within the above range, an optical glass suitable for a lens material capable of excellent chromatic aberration correction can be obtained when combined with a lens made of low dispersion glass.

  A preferable range of the refractive index nd is 1.83 to 1.90, a more preferable range is 1.83 to 1.88, a further preferable range is 1.84 to 1.855, and a preferable range of the Abbe number νd is 23 to 29, a more preferable range is 24 to 25.5, and a further preferable range is 24.5 to 25.25.

  When the refractive index is excessively increased or the Abbe number νd is excessively decreased, the glass stability tends to decrease or the glass transition temperature tends to increase.

[Glass-transition temperature]
The glass transition temperature of the optical glass of the present invention is less than 530 ° C, preferably 520 ° C or less, more preferably 515 ° C or less, and further preferably 510 ° C or less. As the glass transition temperature decreases, the press molding temperature can be set lower. The progress speed of the interface reaction between the glass and the press mold during precision press molding is greatly influenced by the press molding temperature. Therefore, the interface reaction can be significantly suppressed by simply reducing the glass transition temperature by several degrees C. or tens of degrees C.

  In general, when the refractive index is increased, the glass transition temperature tends to increase, but according to the present invention, a glass having a low glass transition temperature suitable for precision press molding can be obtained while being a high refractive index glass.

[Liquid phase temperature]
The liquidus temperature of the optical glass of the present invention is 1080 ° C. or lower, preferably 1060 ° C. or lower, more preferably 1020 ° C. or lower, and further preferably 1015 ° C. or lower.

  By maintaining the liquidus temperature low, the temperature at which the molten glass is formed can be lowered. By keeping the molding temperature low, volatilization of easily volatile components such as boric acid and alkali metals from the surface of the molten glass can be suppressed, and variations in optical properties and surface striae can be suppressed.

  In general, when the refractive index is increased, the liquidus temperature tends to increase, but according to the present invention, a glass having a low liquidus temperature excellent in mass productivity can be obtained while being a high refractive index glass.

  In general, it is difficult to simultaneously achieve a high refractive index, a low glass transition temperature, and a low liquidus temperature. However, according to the present invention, these three characteristics can be realized simultaneously.

[Partial dispersibility]
In order to perform high-order achromatization in an imaging optical system, a projection optical system, etc., it is effective to use a combination of a low dispersion glass lens and a high dispersion glass lens. However, many low-dispersion glass has a large partial dispersion ratio, so when correcting higher-order chromatic aberration, in addition to high dispersion characteristics, combining with lenses that use glass with a small partial dispersion ratio It is valid.

  The present invention provides a high-refractive index, high-dispersion optical glass suitable for correcting high-order chromatic aberration with a small partial dispersion ratio.

  The partial dispersion ratio Pg, F is expressed as (ng−nF) / (nF−nc) using the refractive indexes ng, nF, and nc in the g-line, F-line, and c-line.

Partial dispersion ratio Pg, the partial dispersion ratio on the normal line serving as the reference of a normal partial dispersion glass in F- Abbe's number νd diagram Pg, expressed as ^{F (0), Pg, F} (0) is used Abbe number νd Is expressed by the following equation.
Pg, F ⁽⁰⁾ = 0.6483- (0.0018 × νd)

ΔPg, F is a deviation of the partial dispersion ratio Pg, F from the normal line, and is expressed by the following equation.
ΔPg, F = Pg, F−Pg, F ⁽⁰⁾
= Pg, F + (0.0018 × νd) −0.6483

  In the optical glass of the present invention, the deviation ΔPg, F of the partial dispersion ratio Pg, F is 0.014 or less, preferably 0.013 or less, more preferably 0.012 or less. It is a suitable glass. The partial dispersion ratio Pg, F of the optical glass of the present invention is 0.610 to 0.620, preferably 0.611 to 0.618.

[Manufacture of optical glass]
The optical glass of the present invention weighs and prepares oxides, carbonates, sulfates, nitrates, hydroxides and the like as raw materials so that the desired glass composition is obtained, and mixes well to form a mixed batch. It can be obtained by heating and melting in a melting container, defoaming and stirring to make a molten glass that is homogeneous and does not contain bubbles, and is molded. Specifically, it can be made using a known melting method.

[Preform for precision press molding]
Next, the precision press molding preform of the present invention will be described.
The precision press-molding preform of the present invention comprises the above-described optical glass of the present invention.

  The above-mentioned preform for precision press molding (hereinafter referred to as “preform”) means a glass lump used for precision press molding, and is a glass molded body corresponding to the mass of a precision press molded product.

The preform will be described in detail below.
Preform means a glass preform that is heated and used for precision press molding. Here, precision press molding is also known as mold optics molding, and presses the optical functional surface of an optical element. In this method, the molding surface of the molding die is transferred. The optical function surface means a surface that refracts, reflects, diffracts, or enters and exits the light to be controlled in the optical element, and the lens surface of the lens corresponds to the optical function surface.

To prevent the reaction and fusion between the glass and the press mold surface during precision press molding, the mold surface is coated with a release film so that the glass extends along the molding surface. It is preferable. As a type of release film,
Precious metals (platinum, platinum alloys)
Oxides (Si, Al, Zr, La, Y oxides, etc.)
Nitride (B, Si, Al nitride, etc.)
Examples include carbon-containing films. The carbon-containing film is preferably a film containing carbon as a main component (when the element content in the film is expressed in atomic%, the carbon content is higher than the content of other elements). Specifically, a carbon film, a hydrocarbon film, etc. can be illustrated. As a method for forming a carbon-containing film, a known method such as a vacuum deposition method using a carbon raw material, a sputtering method, an ion plating method, or a thermal decomposition using a material gas such as a hydrocarbon is used. Use it. Other films can be formed using a vapor deposition method, a sputtering method, an ion plating method, a sol-gel method, or the like.

  The preform is produced through a process of heating and melting a glass raw material to produce a molten glass, and molding the molten glass.

  A first production example of a preform is a method of separating a molten glass lump of a predetermined weight from the molten glass and cooling it, and molding a preform having a mass equal to the molten glass lump. For example, glass raw material is melted, clarified, and homogenized to prepare a homogeneous molten glass, which is then discharged from a temperature-adjusted platinum or platinum alloy outflow nozzle or outflow pipe. When molding a small preform or a spherical preform, molten glass is dropped as a molten glass droplet of a desired mass from an outflow nozzle, and it is received by a preform mold and molded into a preform. Alternatively, a preform is formed by dropping a molten glass droplet having a desired mass into liquid nitrogen or the like from an outflow nozzle. When producing medium-sized and large-sized preforms, the molten glass flow is caused to flow down from the outflow pipe, the tip of the molten glass flow is received by the preform mold, and the constricted portion is formed between the nozzle of the molten glass flow and the preform mold. After forming the preform, the preform mold is rapidly lowered directly, the molten glass flow is separated at the constricted portion by the surface tension of the molten glass, and the molten glass lump of a desired mass is received by the receiving member and molded into the preform. .

  In order to manufacture a preform having a smooth surface free from scratches, dirt, wrinkles, surface alteration, etc., for example, a free surface, the molten glass lump is applied to the molten glass lump on the preform mold while being floated while being floated. A method of forming into a preform or a method of forming a preform by putting molten glass droplets in a liquid medium by cooling a gaseous substance at room temperature and normal pressure such as liquid nitrogen is used.

  When the molten glass lump is formed into a preform while floating, a gas (called floating gas) is blown onto the molten glass lump and an upward wind pressure is applied. At this time, if the viscosity of the molten glass lump is too low, the floating gas enters the glass and remains as foam in the preform. However, by setting the viscosity of the molten glass lump to 3 to 60 dPa · s, the glass lump can be levitated without the levitation gas entering the glass.

Examples of the gas used when the floating gas is blown onto the preform include air, N ₂ gas, O ₂ gas, Ar gas, He gas, and water vapor. The wind pressure is not particularly limited as long as the preform can float without coming into contact with a solid such as the mold surface.

  Since many precision press-molded products (for example, optical elements) manufactured from a preform have a rotationally symmetric axis like a lens, the shape of the preform is preferably a shape having a rotationally symmetric axis. As a specific example, one having a sphere or one axis of rotational symmetry can be shown. A shape having one rotationally symmetric axis has a smooth outline with no corners or depressions in the cross section including the rotationally symmetric axis, for example, an ellipse whose short axis coincides with the rotationally symmetric axis in the cross section is defined as the outline. One of the two intersections of the surface and the rotationally symmetric axis, with the shape of a flattened sphere (one axis passing through the center of the sphere and the dimension reduced in the axial direction) A shape including a concave surface, a surface including the other intersection point is a convex surface, and a shape including both surfaces including the two intersection points are concave surfaces.

  In the second preparation example of the preform, a homogeneous molten glass is cast into a mold and molded, and then the distortion of the molded body is removed by annealing, cut or cleaved, and divided into predetermined dimensions and shapes. A glass piece is prepared, the glass piece is polished to smooth the surface, and a preform made of glass having a predetermined mass is obtained. It is preferable to use the preform thus prepared by coating the surface of the preform with a carbon-containing film.

[Optical element]
Next, the optical element of the present invention will be described. The optical element of the present invention is characterized by comprising the above-described optical glass of the present invention. Specifically, lenses such as aspheric lenses, spherical lenses, or plano-concave lenses, plano-convex lenses, biconcave lenses, biconvex lenses, convex meniscus lenses, concave meniscus lenses, micro lenses, lens arrays, lenses with diffraction gratings, prisms, lenses An example is a prism with a function. If necessary, an antireflection film, a wavelength selective partial reflection film, or the like may be provided on the surface.

  Since the optical element of the present invention is made of glass having high dispersion characteristics and a small partial dispersion ratio, high-order chromatic aberration correction can be performed by combining with an optical element made of other glass. Moreover, since the optical element of the present invention is made of glass having a high refractive index, the optical system can be made compact by using it in an imaging optical system, a projection optical system, and the like.

[Method for Manufacturing Optical Element]
Next, the manufacturing method of the optical element of this invention is demonstrated.
The method for producing an optical element of the present invention comprises a step of heating the above-described preform for precision press molding of the present invention and performing precision press molding using a press mold.

  The heating and pressing process of the press mold and the preform is performed in order to prevent oxidation of the molding surface of the press mold or the release film provided on the molding surface, nitrogen gas or a mixed gas of nitrogen gas and hydrogen gas, etc. It is preferable to carry out in a non-oxidizing gas atmosphere. In the non-oxidizing gas atmosphere, the carbon-containing film covering the preform surface is not oxidized, and the film remains on the surface of the precision press-molded product. This film should be finally removed, but in order to remove the carbon-containing film relatively easily and completely, the precision press-molded product may be heated in an oxidizing atmosphere, for example, air. The oxidation and removal of the carbon-containing film should be performed at a temperature at which the precision press-molded product is not deformed by heating. Specifically, it is preferably performed in a temperature range below the glass transition temperature.

In precision press molding, a press mold in which the molding surface has been processed to a desired shape with high accuracy is used in advance, but a mold release film is formed on the molding surface to prevent glass fusion during pressing. Also good. Examples of the release film include a carbon-containing film, a nitride film, and a noble metal film. As the carbon-containing film, a hydrogenated carbon film, a carbon film, and the like are preferable. In precision press molding, after a preform is supplied between a pair of opposed upper and lower molds whose molding surfaces are precisely shaped, the viscosity of the glass reaches a temperature equivalent to 10 ⁵ to 10 ⁹ dPa · s. Both the mold and the preform are heated to soften the preform, and this is pressure-molded to precisely transfer the molding surface of the mold to glass.

Also, a preform whose temperature has been raised to a temperature corresponding to 10 ⁴ to 10 ⁸ dPa · s in advance is supplied between a pair of opposed upper and lower molds whose molding surfaces are precisely shaped. And by pressing this, the shaping | molding surface of a shaping | molding die can be accurately transcribe | transferred to glass.

The pressure and time at the time of pressurization can be appropriately determined in consideration of the viscosity of the glass and the like. For example, the press pressure can be about 5 to 15 MPa, and the press time can be 10 to 300 seconds.
The pressing conditions such as pressing time and pressing pressure may be appropriately set within a known range in accordance with the shape and dimensions of the molded product.

  Thereafter, the mold and the precision press-molded product are cooled, and when the temperature is preferably equal to or lower than the strain point, the mold is released and the precision press-molded product is taken out. In order to precisely adjust the optical characteristics to a desired value, the annealing conditions of the molded product during cooling, for example, the annealing rate may be adjusted as appropriate.

  The manufacturing method of the optical element can be roughly divided into the following two methods. The first method is a method of manufacturing an optical element that introduces a preform into a press mold and heats the mold and the glass material together. When emphasizing improvement in molding accuracy such as surface accuracy and eccentricity accuracy, This is the recommended method. The second method is a method of manufacturing an optical element in which a preform is heated, introduced into a preheated press mold, and precision press-molded, and is recommended when emphasizing productivity improvement.

  The optical element of the present invention can be produced without going through a press molding process. For example, casting a homogeneous molten glass into a mold to form a glass block, annealing to remove the distortion, and adjusting the annealing conditions to adjust the optical characteristics so that the refractive index of the glass becomes a desired value Then, the glass block can be cut or cleaved to make a glass piece, which is then ground and polished to finish the optical element.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Example 1
Using the corresponding oxides, carbonates, sulfates, nitrates, hydroxides, etc. as raw materials for introducing each component so that the glass compositions shown in Tables 1 to 7 are obtained, the raw materials are weighed and sufficiently To prepare a blended raw material, which was put in a platinum crucible, heated and melted. After melting, the molten glass is poured into a mold, allowed to cool to near the glass transition temperature, immediately placed in an annealing furnace, annealed for about 1 hour in the glass transition temperature range, and then allowed to cool to room temperature in the furnace. , Glass No. 1-No. 47 optical glasses were obtained.
In the obtained optical glass, crystals that could be observed with a microscope did not precipitate.
Tables 1 to 7 show the characteristics of the optical glass thus obtained.

Various characteristics of the optical glass were measured by the following methods.
(1) Refractive indexes nd, ng, nF, nc and Abbe number νd
Refractive indexes nd, ng, nF, nc, and Abbe number νd were measured by the refractive index measurement method of the Japan Optical Glass Industry Association standard for the glass obtained by cooling at a temperature drop rate of −30 ° C./hour.
(2) Liquidus temperature LT
The glass was placed in a furnace heated to a predetermined temperature and held for 2 hours. After cooling, the inside of the glass was observed with a 100 × optical microscope, and the liquidus temperature was determined from the presence or absence of crystals.
(3) Glass transition temperature Tg
It measured with the differential scanning calorimeter (DSC) as the temperature increase rate of 10 degree-C / min.
(4) Partial dispersion ratio Pg, F
The refractive index was calculated from ng, nF, and nc.
(5) Deviation of the partial dispersion ratio from the normal line ΔPg, F
It was calculated from the partial dispersion ratio Pg, F ⁽⁰⁾ on the normal line calculated from the partial dispersion ratio Pg, F and the Abbe number νd.

(Comparative Example 1)
When the glass was melted by the method described in the literature so as to have the compositions of Examples 1 to 13 of Patent Document 2, the melt was devitrified during stirring for Examples 1 and 2, and Example 4 was obtained. About 13 did not vitrify. In Example 3, glass was obtained by casting the melt into a mold, but precipitation of crystals was observed inside.

(Example 2)
Melting, clarifying and homogenizing the glass raw material prepared so that each optical glass produced in Example 1 is obtained, making a molten glass, dropping a molten glass drop from a platinum nozzle, and receiving with a preform mold, It was formed into a spherical preform made of the above-mentioned various glasses while being floated by applying wind pressure.

In addition, the molten glass is continuously discharged from the platinum pipe, the lower end of the molten glass is received by a preform mold, a constricted portion is formed in the molten glass flow, and then the preform mold is rapidly lowered directly below the molten glass. The flow was cut at the constricted portion, the molten glass lump separated on the preform mold was received, and molded into preforms made of the above-mentioned various glasses while being floated by applying wind pressure.
The resulting preform was optically homogeneous and of high quality.

(Example 3)
The molten glass prepared in Example 2 was continuously flowed out, cast into a mold, formed into a glass block, annealed, and cut to obtain a plurality of glass pieces. These glass pieces were ground and polished to prepare preforms made of the various glasses.
The resulting preform was optically homogeneous and of high quality.

Example 4
The preforms produced in Examples 2 and 3 were introduced into a press mold including a SiC upper and lower mold and a body mold, in which the surface of the preform was coated with a carbon-containing film and a carbon-based release film was provided on the molding surface. A mold and preform are heated together in an atmosphere to soften the preform, precision press-molded and aspherical convex meniscus lens, aspherical concave meniscus lens, aspherical biconvex lens, aspherical both Various lenses of concave lenses were prepared. In addition, each condition of precision press molding was adjusted in the above-mentioned range.

  When the various lenses thus prepared were observed, no white turbidity due to phase separation was observed, and no scratches, spiders, or damages were observed on the lens surface.

  This process was repeated and mass production tests of various lenses were carried out. However, defects such as glass and press mold fusion did not occur, and high-quality lenses on both the surface and inside could be produced with high precision. . The surface of the lens thus obtained may be coated with an antireflection film.

  Next, the preform coated with the carbon-containing film is heated and softened, separately introduced into a preheated press mold, and precision press-molded to form an aspherical convex meniscus lens, an aspherical concave meniscus lens, Various lenses such as an aspheric biconvex lens and an aspheric biconcave lens were produced. In addition, each condition of precision press molding was adjusted in the above-mentioned range.

  When the various lenses thus prepared were observed, no white turbidity due to phase separation was observed, and no scratches, spiders, or damages were observed on the lens surface.

  This process was repeated and mass production tests of various lenses were carried out. However, defects such as glass and press mold fusion did not occur, and high-quality lenses on both the surface and inside could be produced with high precision. . The surface of the lens thus obtained may be coated with an antireflection film.

  Various shapes of optical elements such as prisms, microlenses, and lens arrays can be produced by appropriately changing the shape of the molding surface of the press mold.

(Comparative Example 2)
Next, the optical glass shown in Table 8 was produced, and a precision press-molding preform was produced using this glass. Then, as in Example 4, this preform was precision press-molded to produce a lens. As a result, many foams were observed on the lens surface. A photograph of the lens surface enlarged is shown in FIGS.

(Example 5)
Using each lens produced in Example 4, various interchangeable lenses for a single-lens reflex camera incorporating each lens were produced.

  Furthermore, various optical systems of a compact digital camera were produced using the lenses produced in Example 4 and modularized. Furthermore, an image sensor such as a CCD or CMOS was attached to these optical systems to form a module.

  Thus, by using the various lenses produced in Example 4, a high-function, compact optical system, an interchangeable lens, a lens module, and an imaging device can be obtained. By combining the lens manufactured in Example 4 and a lens made of high refractive index and low dispersion optical glass, various optical systems in which higher-order chromatic aberration correction is performed and an imaging apparatus including the optical system can be obtained.

  The optical glass of the present invention is an optical glass having a high refractive index, a high dispersion characteristic, excellent devitrification resistance, a low glass transition temperature, and suitable for precision press molding. Further, it is an optical glass suitable for high-order chromatic aberration correction, and is suitably used for producing a precision press molding preform and an optical element.

Claims (26)

Oxide glass, expressed as cation%,
Si ⁴⁺ and B ³⁺ in total 20 to 40%,
Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ in total 15-40%,
Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ in total 0.2 to 20%,
Li ⁺ , Na ⁺ and K ⁺ in total 15-55%,
Including
The cation ratio of the content of B ³⁺ to the total content of B ³⁺ and Si ⁴⁺ is 0.01 to 0.5,
The cation ratio of the Zr ⁴⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ and Zr ⁴⁺ is 0.05 or less,
The molar ratio of the total content of Zn ²⁺ and Ba ^{2+ to} the total content of Zn ²⁺ , Ba ²⁺ , Sr ²⁺ and Ca ²⁺ is 0.8-1;
An optical glass having a refractive index nd of 1.815 or more and an Abbe number νd of 29 or less. The optical glass according to claim 1, wherein the glass transition temperature is less than 530 ° C. The optical glass according to claim 1 or 2, wherein the liquidus temperature is 1080 ° C or lower. Nb ⁵⁺ and ^{Ti 4+} content of the cation ratio of ^{Nb 5+} to the total content of ^{(Nb 5+ / (Nb 5+ +} Ti 4+)) is optical glass according to any one of claims 1 to 3 is from 0.65 to 1 . The optical glass according to claim 1, wherein the content of Si ⁴⁺ is 15 to 30%. The optical glass according to any one of claims 1 to 5, wherein the content of B ³⁺ is 15% or less. The optical glass according to claim 1, wherein the content of Nb ⁵⁺ is 10 to 30%. The optical glass according to claim 1, wherein the content of Ti ⁴⁺ is 0 to 15%. The optical glass according to claim 1, wherein the content of W ⁶⁺ is 0 to 4%. The optical glass according to claim 1, wherein the content of Zr ⁴⁺ is 0 to 4%. The optical glass according to claim 1, wherein the content of Zn ²⁺ is 9% or less. The optical glass according to claim 1, wherein the content of Ba ²⁺ is 6% or less. The optical glass according to claim 1, wherein the content of Sr ²⁺ is 2% or less. The optical glass according to claim 1, wherein the content of Ca ²⁺ is 3% or less. The optical glass according to claim 1, wherein the content of Li ⁺ is 25% or less. The optical glass according to claim 1, wherein the content of Na ⁺ is 30% or less. The optical glass according to claim 1, wherein the K ⁺ content is 25% or less. The optical glass according to any one of claims 1 to 17, wherein a cation ratio of a content of Li ⁺ to a total content of Li ⁺ , Na ⁺ and K ⁺ is 0.1 to 1. The optical glass according to claim 1, wherein ΔPg, F is 0.0130 or less. A precision press-molding preform comprising the optical glass according to claim 1. The manufacturing method of the precision press molding preform which produces the preform of Claim 20 through the process of heating and fusing a glass raw material, producing a molten glass, and shape | molding the said molten glass. An optical element made of the optical glass according to claim 1. A method for manufacturing an optical element, comprising: heating the precision press-molding preform according to claim 20 and performing precision press-molding using a press mold. 24. The method of manufacturing an optical element according to claim 23, wherein the precision press molding preform and the press mold are heated together to perform precision press molding. 24. The method of manufacturing an optical element according to claim 23, wherein the precision press-molding preform is heated and then introduced into a preheated press mold to perform precision press molding. An imaging device comprising the optical element according to claim 22.